In an update on its web site, Ol Pejeta warned that Sudan — the 45-year-old rhino that represents the last male of its kind — is “deteriorating” due to an age-related infection.

“His future is not looking bright,” said the conservancy. “We are very concerned about him – he’s extremely old for a rhino and we do not want him to suffer unnecessarily.”

Sudan developed an infection on his rear right leg toward the end of last year. Veterinarians treated the infection, which seemed to heal: Sudan was back to his normal habits in January. But in the second half of February, his behavior shifted and vets found “a secondary and much deeper infection”, which is not responding well to treatment. The conservancy has launched a last ditch fundraising appeal for the species.

If Sudan doesn’t pull through, it means the two female northern white rhinos at Ol Pejeta — Fatu and Najin — will be the only two remaining individuals of their subspecies, Ceratotherium simum cottoni. Ol Pejeta protects all of the rhinos under 24-hour armed guard.

The northern white rhino once ranged across parts of Uganda, South Sudan, Central African Republic, and Democratic Republic of the Congo but was hard hit by poaching. By the early 1980s, the population was down to double digits.